Ultrasonic Surgical Handpiece Having a Thermal Diffuser

ABSTRACT

An ultrasonic surgical handpiece comprising a thermal diffuser that includes a thermal conductive layer and an electrical insulating layer. The thermal diffuser reduces hot spots that are objectionable to the user. The handpiece may also comprise an anti-rotation feature which distributes force of the metal horn applied to the polymer housing by increasing applied area under torque.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation patent application of and claimspriority and benefit under 35 U.S.C. § 120 to copending U.S. patentapplication Ser. No. 15/813,899 filed on Nov. 15, 2017, which claimspriority to and benefit under 35 U.S.C. § 119 to U.S. ProvisionalApplication No. 62/422,635, filed Nov. 16, 2016, the entire contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate generally to surgicalhandpieces, for example, handpieces in ultrasonic surgical aspiratorsystems for tissue ablation.

Ultrasonic aspiration has become the standard of care for removal oftumors and diseased tissue in neurosurgery and general surgery.Ultrasonic aspirators are used for ultrasonic fragmentation of tissue atan operation site and aspiration of the tissue particles and fluid awayfrom the site. Typically, ultrasonic surgical aspirators include anultrasonic transducer supported within a handpiece, an ultrasonicallyvibrating horn or tip operably connected to the ultrasonic transducer,and a sleeve or flue positioned about the horn. The horn includes alongitudinally extending central bore having one end located adjacent adistal tip and a second end located adjacent the proximal end of thehorn. The proximal end of the horn is adapted to engage a vacuum sourceto facilitate aspiration of fluid. The flue is positioned about the hornto define an annular passage. Irrigation fluid is supplied through theannular passage around the horn to the surgical site where it mixes withblood and tissue particles and is aspirated through the bore in thehorn. By mixing the irrigation fluid with the blood and tissueparticles, coagulation of the blood is slowed down and aspirationthereof is aided. When the longitudinally vibrating tip in such anaspirator is brought into contact with tissue, it gently, selectively,and precisely fragments and removes the tissue. U.S. Pat. Nos. 5,015,227and 4,988,334 disclose such ultrasonic surgical devices and areincorporated herein by reference. A known ultrasonic aspirator on themarket is the CUSA® Excel Ultrasonic Surgical Aspirator (IntegraLifeSciences Corporation, Plainsboro, N.J., U.S.A.).

The handpiece typically has a housing encasing a transducer on which asurgical tip is fastened. The housing is commonly made of a polymericmaterial for electrical safety, especially with high-voltageelectrosurgery levels (e.g., 1750 Vp) applied to the metallic body ofthe transducer and surgical tip. CUSA Excel 36 kHz handpiece isdescribed in U.S. Pat. No. 6,214,017 to Stoddard, et al., and 23 kHzhandpiece is described in U.S. Pat. Nos. 4,425,115 and 4,223,676 toWuchinich et al.

Polymer housings of the handpieces in existing systems yieldedconcentrated thermal rise associated with the transducer, or so called“hot spots” that are felt by the surgeon whose hand tactile sensitivityis acute during surgery. Ultrasonic transducers with metallic housingsdo not have these complications due to strength and diffusion of hotspots with thermally conductive cases, but the electrical safetyrequirements given simultaneous ultrasonic and electosurgery powerapplication necessitate polymer housings.

In addition, polymer housings sometimes failed due to rotation of thetransducer, as a result of low-allowed stress of plastic andconcentrated stress of mating metallic anti-rotation constraints. Thecommercial CUSA Excel 36 kHz handpiece is magnetostrictive and has a hexfeature that can fail under misuse, such as the nurse tightening orloosening the surgical tip while only holding the internal horn with thehousing. Many of the failed handpieces are twisted in the housing. Thetransducer vibrates along its length and stepped horns and specialtyprofiles of reduced diameter amplify vibration. Often, the surgical tipis a single use device which must be attached under high torque (e.g.25-65 in-lb) to the internal ultrasonic horn of the transducer to ensureadequate acoustic coupling. The internal ultrasonic horn of thetransducer commonly has flats or hex features, such as a nut, forholding the transducer while tightening the surgical tip with a specialtorque wrench. In addition, a torque base is provided as a platform tohold the handpiece for fastening and loosening a surgical tip. It isfound in practice that sometimes the nurse or clinician does not employthe torque base to hold the transducer while tightening the surgical tipbefore use or loosening it following the procedure. Piezoelectrictransducers have PZT (lead-zirconate-titanate) ceramics that areelectrically connected by wires to external cables, which can break whentwisted. Magnetostrictive transducers depend on positioning of thetransducer stack in the magnetic field to ensure adequate power.Effective anti-rotation constraints are needed, but these must notrigidly couple ultrasound during vibration to the housing, because ofloss of power, errant heating, and potential for audible noise fromsub-harmonics. Hex features alone on internal horns with matinghexagonal recesses on housings could fail structurally at the appliedtorque needed for surgical tips.

Hence, those skilled in the art have recognized a need for surgicalhandpieces with improved thermal performance and structural stability.Embodiments of the present invention fulfill this need and others.

SUMMARY OF THE INVENTION

Briefly and in general terms, embodiments of the present inventiondisclose high-powered compact ultrasonic transducers with electrosurgerycoagulation that incorporate a conductive thermal diffuser to eliminateobjectionable hot spots from the surgeon's hands in prolonged usage,such as in brain tumor removal and liver resection.

In some embodiments of the invention, for example, a surgical handpiecemay comprise a housing, an electrical component within the housing,and/or a thermal diffuser disposed between the housing and theelectrical component and comprising a thermal conductive layer and anelectrical insulating layer. In various embodiments, the thermalconductive layer may be closer to the housing than the electricalinsulating layer.

In addition, in various embodiments, the thermal conductive layer maycomprise a plurality of thermal conductive material pieces. In someembodiments, there may be an overlap between two thermal conductivematerial pieces. In various embodiments, the housing may have anelongated body and the thermal diffuser may be in a cylindrical orpartially cylindrical form that fits in the elongated body around theelectrical component. Moreover, in some embodiments, the thermalconductive layer may be made of a material selected from the groupconsisting of copper, aluminum, nickel, silver, gold and alloys thereof.In various embodiments, the electrical insulating layer may be made of amaterial selected from the group consisting of polytetrafluoroethylene,polycarbonate, polypropylene and combinations thereof. In someembodiments, the thermal conductive layer and the electrical insulatinglayer may be bonded with an adhesive. In various embodiments, thehousing may be made of an electrical insulating material. In addition,in some embodiments, the electrical component may be an ultrasonicallypowered transducer.

In some embodiments, a surgical handpiece may comprise a housing havingan elongated body along a longitudinal axis. In various embodiments, anultrasonically powered transducer may be positioned within the elongatedbody of the housing. In addition, in some embodiments, a thermaldiffuser may be disposed between the elongated body of the housing andthe transducer. In various embodiments, the thermal diffuser maycomprise a thermal conductive layer and an electrical insulating layer.In some embodiments, the thermal conductive layer may be closer to theelongated body of the housing than the electrical insulating layer. Invarious embodiments, the thermal diffuser may be disposed adjacent theelongated body of the housing and may be radially spaced outwardly fromthe transducer.

In addition, in various embodiments, the thermal conductive layer maycomprise a plurality of thermal conductive material pieces. In someembodiments, there may be an overlap between two thermal conductivematerial pieces. In various embodiments, the thermal conductive layermay be made of at least copper and the electrical insulating layer maybe made of at least polytetrafluoroethylene. Moreover, in someembodiments, the thermal conductive layer and the electrical insulatinglayer may be bonded with an adhesive.

In various embodiments, an ultrasonic surgical handpiece may comprise anelongated housing having an inner surface, a longitudinal axis, and/or ahousing engagement portion on the inner surface. In some embodiments,the housing engagement portion may have a transverse section thatincludes a central recess, a plurality of pointed recesses pointingradially outward from the central recess and spaced evenly about thelongitudinal axis, and/or convex arcs joining adjacent pointed recesses.In various embodiments, an ultrasonic horn may be contained coaxiallywithin the housing and include an outer surface and a horn engagementportion on the outer surface. Moreover, in some embodiments, the hornengagement portion may have a transverse section that includes a centralportion, a plurality of pointed protrusions extending radially outwardand spaced evenly about the longitudinal axis, and/or concave arcsjoining adjacent pointed protrusions. In various embodiments, each ofthe pointed protrusions may correspond in shape and may be engageablewith each of the pointed recesses.

In some embodiments, each convex arc may have a side wall which isgenerally parallel with the longitudinal axis, and each concave arc mayhave a side wall which is generally parallel with the longitudinal axis.In various embodiments, the housing engagement portion may comprise atleast three pointed recesses, and the horn engagement portion maycomprise at least three pointed protrusions. In some embodiments, thehousing engagement portion may comprise five to seven pointed recesses,and the horn engagement portion may comprise five to seven pointedprotrusions. In addition, in some embodiments, at least one pointedrecess may have a recess tip portion that is rounded or curved orconstitutes a portion of a sphere. In various embodiments, at least onepointed protrusion may have a protrusion tip portion that is rounded orcurved or constitutes a portion of a sphere.

In accordance with aspects of some embodiments of the present invention,there is provided a surgical handpiece which comprises a housing, anelectrical component within the housing, and a thermal diffuser disposedbetween the housing and the electrical component. The thermal diffusercomprises a thermal conductive layer and an electrical insulating layer,wherein the thermal conductive layer is closer to the housing than theelectrical insulating layer. In more detailed aspects, the thermalconductive layer comprises a plurality of thermal conductive materialpieces, and there is an overlap between two thermal conductive materialpieces.

In further detailed aspects, the housing of the surgical handpiece hasan elongated body and the thermal diffuser is in a cylindrical orpartially cylindrical form that fits in the elongated body around theelectrical component.

In accordance with other aspects of embodiments of the presentinvention, an anti-rotation feature is provided for distributing forceof the metal horn applied to the polymer housing by increasing appliedarea under torque, thereby reducing failure of surgical devices due torotation of the transducer during tightening or loosening of surgicaltips.

In more detailed aspects, there is provided an ultrasonic surgicalhandpiece which comprises an elongated housing having an inner surface,a longitudinal axis, and a housing engagement portion on the innersurface, the housing engagement portion having a transverse section thatincludes a central recess, a plurality of pointed recesses pointingradially outward from the central recess and spaced evenly about thelongitudinal axis, and convex arcs joining adjacent pointed recesses; anultrasonic horn contained coaxially within the housing and having anouter surface and a horn engagement portion on the outer surface, thehorn engagement portion having a transverse section that includes acentral portion, a plurality of pointed protrusions extending radiallyoutward and spaced evenly about the longitudinal axis, and concave arcsjoining adjacent pointed protrusions; and wherein each of the pointedprotrusions corresponds in shape and is engageable with each of thepointed recesses.

In a further detailed aspect, each convex arc of the housing engagementportion has a side wall which is generally parallel with thelongitudinal axis, and each concave arc of the horn engagement portionhas a side wall which is generally parallel with the longitudinal axis.In addition, at least one pointed recess may have a recess tip portionconstituting a portion of a sphere, and at least one pointed protrusionmay have a protrusion tip portion constituting a portion of a sphere.

Other features and advantages of the embodiments of the presentinvention will become more apparent from the following detaileddescription of the invention, when taken in conjunction with theaccompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention.

Embodiments of the present invention are described herein with referenceto the drawings, in which:

FIG. 1 is a perspective view of an ultrasonic surgical apparatus inaccordance with embodiments of the present invention;

FIG. 2 is a side view of an ultrasonic surgical handpiece in accordancewith embodiments of the present invention with a nosecone and surgicaltip attached to it;

FIG. 3 is a longitudinal-sectional view of the ultrasonic surgicalhandpiece of FIG. 2;

FIG. 4 is another longitudinal-sectional view of a portion of theultrasonic surgical handpiece of FIG. 2;

FIG. 5 is a perspective view of a portion of the ultrasonic surgicalhandpiece of FIG. 2 with the handpiece housing shown in phantom;

FIG. 6 is a perspective view of a thermal diffuser in accordance withembodiments of the present invention;

FIG. 7 is a cross-sectional view of the thermal diffuser of FIG. 6;

FIG. 8 is a side view of the thermal diffuser of FIG. 7;

FIG. 9A is a top plan view of a polytetrafluoroethylene (PTFE) layer ofa thermal diffuser composite sheet in accordance with embodiments of thepresent invention;

FIG. 9B is a side view of the PTFE layer of FIG. 9A;

FIG. 10A is a top plan view of a copper tape component of the thermaldiffuser composite sheet;

FIG. 10B is a side view of the copper tape component of FIG. 10A;

FIG. 11A is a top plan view of another copper tape component of thethermal diffuser composite sheet;

FIG. 11B is a side view of the copper tape component of FIG. 11A;

FIG. 12 illustrates a thermal diffuser composite sheet;

FIG. 13 is a side view of the thermal diffuser composite sheet of FIG.12;

FIG. 14 is a detailed view of a section of the thermal diffuser shown inFIG. 13;

FIG. 15 is a perspective view of a handpiece housing;

FIGS. 16 to 18 illustrate steps of placing a thermal diffuser in thehandpiece housing of FIG. 15;

FIG. 19 shows the test results of handpiece temperatures duringcontinuous operation;

FIG. 20 is a longitudinal-sectional view of an ultrasonic surgicalhandpiece in accordance with embodiments of the present invention;

FIG. 21 is a perspective view of an ultrasonic transducer including aninternal ultrasonic horn in accordance with embodiments of the presentinvention;

FIG. 22 is a perspective view of a portion of the internal ultrasonichorn shown in FIG. 21;

FIG. 23 illustrates a housing engagement portion of a handpiece housing;

FIG. 24 is a longitudinal-sectional view of a portion of the handpiecehousing and internal ultrasonic horn in an assembled state;

FIG. 25 is a cross-section view of the internal ultrasonic horn takenalong line E-E of FIG. 22;

FIG. 26 is a cross-section view of the handpiece housing taken alongline F-F of FIG. 23.

FIG. 27 is a side view of an internal ultrasonic horn;

FIG. 28 is a detailed view of a section of the internal ultrasonic hornof FIG. 27;

FIG. 29 is a cross-sectional view taken along line Z-Z of FIG. 27;

FIG. 30 is a cutaway illustration of a handpiece housing in accordancewith embodiments of the present invention;

FIG. 31 is a cross-sectional view taken along line D-D of FIG. 30;

FIG. 32 is a detailed view of the housing engagement portion of thehandpiece housing shown in FIG. 31; and

FIG. 33 is a cross-sectional view of the housing engagement portionshown in FIG. 32.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the presently disclosed surgical handpieces will now bedescribed in detail with reference to the drawings, in which likereference numerals designate identical or corresponding elements in eachof the several views. As used herein, the term “distal” refers to thatportion of the instrument, or component thereof which is farther fromthe user while the term “proximal” refers to that portion of theinstrument or component thereof which is closer to the user duringnormal use. The terms “ultrasonic horn,” “ultrasonic tip,” “ultrasonicaspirating tip,” “ultrasonic surgical aspirating tip,” “aspirating tip,”“ultrasonic surgical tip,” “surgical tip”, “horn” and “tip” are usedherein interchangeably. The terms “housing,” “handpiece housing,” and“transducer housing” are used herein interchangeably. The terms“internal ultrasonic horn” and “internal horn” are used hereininterchangeably.

FIGS. 1-3 show an ultrasonic surgical apparatus 10 for ultrasonicallyfragmenting and aspirating tissue. Generally the ultrasonic surgicalapparatus 10 includes a handpiece 12 for use by a surgeon to directfragmentation. The handpiece 12 encases a transducer 19 coupled to aninternal ultrasonic horn 11 to which a surgical tip 14 is fastened. Thetransducer converts electrical energy into mechanical motion. Thesurgical tip 14 can be powered by the transducer 19 and beultrasonically actuated to fragment tissue and suction effluent via acentral channel 17. The internal ultrasonic horn 11 includes aconnecting point for the surgical tip 14 and transfers the vibrationsfrom the transducer 19 to the surgical tip 14 to fragment tissue duringsurgery. A distal end portion 13 of a surgical tip 14 extends beyond adistal end of a flue 16. The internal ultrasonic horn 11 and thesurgical tip 14 may be made of titanium or other conventional materialsknown in the art.

A cooling and irrigation system which provides cooling fluid to theultrasonic horn 14 is provided for maintaining temperature within anacceptable range. The handpiece 12 includes a housing 50, which may beformed of a sterilizable plastic, metal or other suitable materials or acombination thereof. The flue 16 provides a path for irrigation fluid orliquid and connects to the distal end of the handpiece 12. The flue 16typically connects to the handpiece 12 via a nosecone 40. The flue 16may include or attach to a flue tube 18. The nosecone 40 connects to thehousing 50 and covers the proximal end portion of the surgical tip 14.

An irrigation tube 22 connects to the flue tube 18 up-stream andsupplies irrigation fluid through the flue tube 18 to an operative siteduring surgery. An aspiration tube 24 provides suction and a path foraspiration from the operative site to a collection canister (not shown).An electrical cable 26 provides power to the apparatus or providesswitching connections.

As shown in FIGS. 4 and 5, the handpiece 12 has an elongated housing 50and an electrical component, such as the ultrasonically poweredpiezoelectric transducer 19, within the housing 50. The handpiece 12also has a thermal diffuser 100 within the housing 50. The thermaldiffuser 100 is disposed between the housing 50 and the electricalcomponent 19. The thermal diffuser 100 is in a cylindrical form or asubstantially or partially cylindrical form that fits in the elongatedbody of the housing 50 around the internal electrical component 19.

The housing has a proximal shoulder 52 and a distal shoulder 54 on theinner surface of the housing. The proximal shoulder 52 faces generallydistally and the distal shoulder 54 faces generally proximally. Theshoulders 52, 54 are formed radially about the longitudinal axis L ofthe housing 50 and form a sitting space in between for the thermaldiffuser 100 to snugly sit in and stay in place around the inner surfaceof the housing 50. The housing is made of a material that is electricalinsulating and preferably also heat resistant. For example, the housingmay be made of polyphenylsulfone.

FIGS. 6 to 14 show an exemplary embodiment of a thermal diffuser of thepresent invention. The thermal diffuser 100 is made from a thermaldiffuser composite sheet 150 that comprises a thermal conductive layer110 and an electrical insulating layer 120. The thermal conductive layer110 comprises thermal conductive material pieces 110 a, 110 b withoverlapping areas 110 c between pieces.

To make the thermal diffuser, take a sheet of an electrical insulatingmaterial 120, such as a sheet of polytetrafluoroethylene (PTFE), ofsuitable dimensions. Take thermal conductive material pieces 110 a, 110b, such as copper foil tape, of suitable dimensions. The thermalconductive material pieces may be of the same or different sizes. Cleanthe PTFE sheet with a cleanser, for example, isopropyl alcohol, toprovide an adhesive ready surface. Lay and bond copper tape pieces onthe adhesive ready surface of PTFE sheet. Do it piece by piece with anoverlapping area 110 c of about 5/16 inches between thermal conductivematerial pieces 110 a, 110 b. All pieces of copper tape on the PTFEsheet are then smoothed by a plastic rod. The edges of the copper tapeor PTFE piece are then cut so that the two layers match in size andshape to provide a thermal diffuser composite sheet 150.

The next steps are to make the thermal diffuser composite sheet 150 intoa thermal diffuser and place it into a handpiece housing. An exemplaryembodiment of a housing is shown in FIG. 15. Bend or roll the thermaldiffuser composite sheet 150 by a plastic rod to form a thermal diffuser100 in a generally cylindrical form as shown in FIG. 16. The thermalconductive layer is the outer layer of the cylinder and the electricalinsulating layer is the inner layer of the cylinder. The strips ofoverlapping areas 110 c extend longitudinally on the thermal diffuser.Then put the thermal diffuser into the housing 50 as shown in FIGS. 17and 18. Optionally, use a heat gun and a plastic rod to smooth thethermal diffuser inside of the transducer housing. Finally, check thedisposition of the thermal diffuser inside of the transducer housing.

The thermal diffuser cylinder tends to spring out in the housing andstays in place in the housing, for example, in the space between theshoulders 52, 54. Once put in the housing, the thermal diffuser cylinderopens, conform to the inner surface of the housing, and stays in placewith the ends touching or nearly touching with a small gap 130, asillustrated in FIG. 18. The thermal conductive layer 110 within thehandpiece is closer to the housing 50 than the electrical insulatinglayer 120. The thermal conductive layer 110 faces the housing 50 and theelectrical insulating layer 120 faces the electrical component 19.

Although the embodiment shown in the drawings has a thermal conductivelayer that comprises three thermal conductive materials pieces, it isunderstood that the thermal conductive layer may comprise or consist ofa single sheet of thermal conductive material or a plurality of thermalconductive material pieces. There may be any suitable amount of overlapbetween thermal conductive material pieces or no overlap at all, andthere may be gaps between thermal conductive material pieces. Likewise,the electrical insulating layer may comprise or consist of a singlesheet of electrical insulating material as illustrated in the drawingsor a plurality of electrical insulating material pieces, and there maybe any suitable amount of overlap between the electrical insulatingmaterial pieces or no overlap at all and there may be gaps between theelectrical insulating material pieces. The thermal conductive layer andthe electrical insulating layer do not need to be perfectly continuouslayers to perform their respective functions. However, it is believedthe embodiment as shown, which includes three thermal conductivematerial pieces with overlapping areas between the pieces, will preventdeformation that may be caused by thermal expansion.

The thermal conductive layer is made of a material that exhibits highthermal conductivity, such as metals, carbons such as graphite, ceramicsand certain composites. Materials of high thermal conductivity arewidely used in heat sink applications. The thermal conductive materialof the thermal conductive layer preferably has a thermal conductivityvalue that is higher than about 90 W/m·K and more preferably higher thanabout 200 W/m·K. Examples of thermal conductive materials includecopper, aluminum, nickel, silver, gold and alloys thereof such asaluminum alloy.

The electrical insulating layer is made of an electrical insulatingmaterial. Electrical insulating materials are typically considered to bematerials with a surface resistivity greater than 10¹² Ω/sq (ohms persquare). Material like glass, porcelain, paper, polymeric materials suchas rubber, rubber-like polymers and plastics, and composite materialsare good electrical insulators. Examples of electrical insultingmaterials include polytetrafluoroethylene (PTFE), polycarbonate,polypropylene, polyetherimide, polyphenylsulfone, and combinationsthereof.

The thermal conductive layer and the electrical insulating layer may bebonded with an adhesive or be connected by mechanical means or othermeans known in the art. If metal tape such as copper tape is used as thethermal conductive layer, no separate adhesive is necessary to bond itwith the electrical insulating layer, as the copper tape is backed withan adhesive that may electrically conductive or non-conductive. It isalso contemplated that the thermal conductive layer and the electricalinsulating layer do not need to be bonded or connected by any adhesiveor particular means. The layers may stay in contact after they arerolled up and inserted into the housing.

Suitable adhesives include, but are not limited to, acrylic, epoxy,aramid-based, urethane-based, polyamide-based, polyethylene-based,ethylene-vinyl acetate (EVA)-based, polyester-based, and polyvinylchloride (PVC)-based adhesives. The layers may also be bonded with anadhesive tape, such as a double-sided adhesive tape.

The exemplary embodiment of the thermal diffuser described above is aPTFE plus copper thermal diffuser. Copper tape with an adhesive side isused as the thermal conductive layer. The copper tape is backed with aPTFE polymer sheet. The copper is placed on the PTFE sheet and keptbetween the housing and PTFE sheet. The PTFE sheet prevents the copperfrom contacting and electrically shorting any of the elements of thetransducer stack, such as the terminal. Additionally, PTFE has lowcoefficient of friction if any elements of the vibrating stack contactthis material, although such contact is avoided by design. The thermaldiffuser can be made from a PTFE sheet having a thickness of about 0.020inches, and a copper foil tape that has a nonconductive adhesive backingand a total thickness of about 0.0029 inches.

The thermal conductive layer, the electrical insulating layer, and thethermal diffuser composite sheet formed from the two layers may have anyappropriate thicknesses as can be readily determined by those skilled inthe art, taking into consideration a number of factors including, butnot limited to, the desired thermal conductive and electrical insulatingproperties, the available space in the handpiece housing to accommodatethe thermal diffuser, and the necessary flexibility of the thermaldiffuser composite sheet to be rolled up to form a generally orsubstantially cylindrical form or any other desired form. For example,the thermal conductive layer may have a thickness of less than about 0.1inches and preferably less than 0.05 inches, for example, in the rangeof from 0.001 to 0.010 inches, and the electrical insulating layer mayhave a thickness of less than about 0.1 inches and preferably less thanabout 0.05 inches, for example, in the range of 0.01 to 0.05 inches.

Suitable dimensions of the thermal diffuser composite sheet and thethermal diffuser formed therefrom can also be readily determined bythose skilled in the art, depending on a number of factors, such as thesize and shape of the medical device that contain the thermal diffuserand the desired thermal diffusing effects. The thermal conductive layerand the electrical insulating layer in a thermal diffuser do not need tomatch perfectly in size or shape so long as they overlap and provideadequate thermal dissipation and prevent short circuiting.

Although as illustrated, the thermal diffuser would be touching theinner surface of the handpiece housing once the thermal diffusercylinder springs out, it is believe that the thermal diffuser would workwithout contact with the housing or the transducer. The thermal diffusermay be bonded to the housing and/or the transducer, but it is notnecessary.

It is also contemplated that the thermal conductive layer and theelectrical insulating may be placed into the housing separately orsequentially. For example, a thermal conductive cylinder may be insertedinto the housing and positioned in place first, and then an electricalinsulating cylinder is inserted into the thermal conductive sleeveformed in the housing. The thermal diffuser may have multiple thermalconductive layers and multiple electrical insulating layers arranged inany suitable order.

After the thermal diffuser composite sheet is rolled up and before thethermal diffuser is placed in the housing, the ends of the thermaldiffuser may be in contact or not in contact or may overlap to variousdegrees. Likewise, after the thermal diffuser is placed in the housing,the ends of the thermal diffuser may be in contact or not in contact ormay overlap to various degrees. The loose end of the thermal diffusermay be bonded to the cylindrical body with an adhesive or by mechanicalor chemical means, but it is not necessary.

Without being bound by any particular theory, it is believed that thecopper is not a simple heat sink, as it is not contacting the thermallyheated elements, such as the terminals, or conducting. Differentthickness layers of copper were tested, but it was learned that a single76 micrometer or 0.003 inch thick sheet with minimal overlap wassufficient. Doubling the thickness had little effect on temperature atthe housing, whereas heat sink size and volume in conventionalelectrical designs, such as for transistor and power supplies, aresurface area and volume dependent and have influence on dissipation ofheat. Instead, the copper, which is thermally conductive, diffusesradiant and convective heat from the hot spots of the transducer stackwhich transits the space between the transducer stack or terminal andthe PTFE sheet to the copper. The concentrated radiant and convectiveheat would attempt to concentrate at the copper, but it is highlythermally conductive so the heat diffuses about the copper. If the heatwere in the form of an electric field or conducted current it woulddiffuse to form an equipotential surface about the whole surface of thecopper. An analogy is that the copper diffuses the heat in a way thatwould be an equipotential temperature. However, some heat is lost to thesurroundings, and some heat still conducts to the housing. The coppersheet is a highly thermally conductive diffuser of concentratedconvective and radiant heat arriving to its surface, thereby reducingthe temperature associate with hot spots.

The benefit of the thermal diffuser is maintained at very high strokesfor a handpiece and surgical tip combination, as exhibited with theelectromechanical data and associated infrared thermal images at 5minutes and 10 minutes of operation. High stroke and surgical tip andassociated stack velocity at ultrasonic frequency are necessary toefficacy in tumor and tenacious tissue removal in neurosurgery andgeneral surgery applications. The functionality of the thermal diffuserwas also maintained at rated life use ratings, and as shown in theelectromechanical data for a transducer tested to two twice liferatings. The transducer is a couple degrees above body temperature attwice rated life, although the stroke has increased marginally frominitial calibration. The temperature at the case is more uniform andasymptotes with time, and is less objectionable to the acute tactilesensitivity of the surgeon. Some test data are shown in FIG. 19. Thethermal diffuser can lower objectionable hot spots of over 55° C. toless than 41° C., and in most cases to about body temperature (37° C.),such that they are not felt by the surgeon.

In addition to incorporation of a thermal diffuser in some embodimentsof the present invention, additional means may be taken to help reducehot spots, for example, by eliminating interfaces that could causeheating under vibration of the stack. This may include removing anyrigid epoxy from vibrating terminals. These terminals contact metallizedelectrodes on the piezoelectric ceramic disks. The terminals arevibrating at the high velocities associated with ultrasonic vibrationand they are also thermally conductive, bringing the heat in the stackcloser to the housing. Damping compounds that are rubber or rubber likemay be placed on the terminals where they are soldered to flexiblehook-up wires. Other means for reducing hot spots include using plasmametal coatings of minimal thickness, e.g. less than 25.4 micrometers of0.001 inch.

Turning now to FIGS. 20 to 33, in accordance with other aspects ofembodiments of the present invention, an ultrasonic surgical handpiecewith an anti-rotation feature is provided. The anti-rotation featurereduces the risk of structural failure. The ultrasonic surgicalhandpiece 12 comprises an elongated housing 50 having an inner surface550, a longitudinal axis L, and a housing engagement portion 500 on theinner surface 550. The housing engagement portion 500 has a transversesection that includes a central recess 540, six pointed recesses 510pointing radially outward from the central recess and spaced evenlyabout the longitudinal axis L, and convex arcs 520 joining adjacentpointed recesses 510. The ultrasonic surgical handpiece 12 alsocomprises an internal ultrasonic horn 11 contained coaxially within thehousing 50 and having an outer surface 450 and a horn engagement portion400 on the outer surface 450. The horn engagement portion 400 has atransverse section that includes a central portion 440, six pointedprotrusions 410 extending radially outward and spaced evenly about thelongitudinal axis L, and concave arcs 420 joining adjacent pointedprotrusions 410. Each of the pointed protrusions 410 corresponds inshape and size and is engageable with each of the pointed recesses 510.Each convex arc 520 has a side wall 530 which is parallel with thelongitudinal axis L, and each concave arc 420 has a side wall 430 whichis parallel with the longitudinal axis L.

Each convex arc is a section of a circle or some other curved shape,such as an ellipse. For example, each convex arc may be an arc of acircle having a radius in the range of about 0.05 to about 1.0 inch andpreferably in the range of about 0.1 to about 0.5 inches. In anexemplary embodiment, each convex arc has a radius of about 0.2 inches.It is possible that the diameter or radius measurements of the pluralityof convex arcs are not identical.

Likewise, each concave arc is a section of a circle or some other curvedshape, such as an ellipse. For example, each concave arc may be an arcof a circle having a radius in the range of about 0.05 to about 1.0 inchand preferably in the range of about 0.1 to about 0.5 inches. In anexemplary embodiment, each convex arc has a radius of about 0.2 inches.It is possible that the diameter or radius measurements of the pluralityof convex arcs are not identical, so long as the concave arcs correspondto and are engageable with the corresponding convex arcs.

At least one of the pointed recesses may have a recess tip portion thatis rounded or curved or constitutes a portion of a sphere. The recesstip portion may have a radius in the range of about 0.005 to about 0.1inches, for example, about 0.01 inches.

At least one of the pointed protrusions may have a protrusion tipportion that is rounded or curved or constitutes a portion of a sphere.The protrusion tip portion may have a radius in the range of about 0.005to about 0.1 inches, for example, about 0.01 inches.

In an anti-rotation system in accordance with embodiments of the presentinvention, the housing engagement portion may comprise a plurality ofpointed recesses, for example, at least 3 and preferably 5-7 pointedrecesses, and the horn engagement portion may comprise a plurality ofpointed protrusions, for example, at least 3 or preferably 5-7 pointedprotrusions. The exemplary embodiment shown in the drawings has sixpointed recesses in the cross-section of the housing engagement portion,and six pointed protrusions in the horn engagement portion. The hornengagement portion that has six pointed protrusions is referred tohereinafter as a “hexacog”.

The hexacog design can be used for effective anti-rotation constraints.Unlike a hex nut, which can appear like an inclined plane withmechanical advantage in rotation, a cog presents a large surface areathat resists rotation while distributing load and resultant stress.Inclined planes provide mechanical advantage for lifting the hex surfaceaway from the mating feature or surface, causing cam-out. The mechanicaladvantage of an inclined plane is intuitive and employed in the earliestof human mechanisms, such as for lifting blocks of pyramids, zippers,and other simple but elegant mechanical systems.

Design of a metal to polymer interface should consider increasing areaunder greater loading such that the resistance to applied torquedistributes and maintains stress under allowed limits. The stress in asimple hex is great, and increases with the mechanical advantage of theinclined plan of the hex, such that the area is reduced as load isapplied. Polymers are forgiving relative to brittle materials in thatlocal plastic deformation can occur conforming the polymer to the metal,rather than cracking under localized stress distribution. In thehexacog, as the 6 cog features cam-into the polymer, the load isdistributed and the area opposing the applied torque becomes greater.The applied area divides the holding force by 6, and causes less stressconcentration. In a cog design, often the material must fail for themechanism to fail. The hexacog overcomes a failure mode of prior arthandpieces, based on the cog railway anti-rotation mechanism. Knownmachining methods make the horn and housing mating geometries practical.The hexacog design was developed based on a fundamental understanding ofthe need to increase load distribution during elastic and local plasticdeformation.

The greater the contact area, the less the stress for a given holdingforce or torque, such as determined by Hooke's Law, σ (stress)=F(Force)/A (Area). It was determined that the cog feature could beintroduced to a starting hex shape. A ball end-mill can be used tocreate the cog in the hex of the internal ultrasonic horn and a broachcan be used to introduce the mating shape to the polymer housing. It wasrecognized that the cog mating features increased contact area underload, rather than allowing cam-out. Additionally, it was found insimulation that the cog mates with the six cogs of the housing, dividingmaximum stress by a factor of 6 and multiplying allowed force forallowed stress by a factor of 6.

When the load due to tightening the surgical tip to the internalultrasonic horn is removed, as it is in operation, the hexacog of theinternal ultrasonic horn is free to vibrate or slide longitudinally andhas only casual contact with the housing. The hexacog feature of theinternal horn is also located close to a node, of minimum vibration, inthe standing wave of the ultrasound.

If the flats 111 of the internal horn are not held during tightening ofthe surgical tip to high torque levels, the hexacog prevents rotation ofthe transducer in the polymer housing. In an exemplary embodiment for a36 kHz transducer, the hexacog is machined in a high cyclic fatigue life6AL 4V titanium material and the mating polymer is polyphenylsulfone(PPSU). It is understood by those skilled in the art that otherelectrically insulating polymers, such as polyetherimide plastic, can beutilized. The hexacog can be implemented for any ultrasonics frequencytransducer, such as 23 kHz, 36 kHz, or 55 kHz transducer.

Other locations of the hexacog along the length of the internal horn andpolymer case are possible, as well as other overall diameters and widthsof the hexacog feature are within the scope of embodiments of thepresent invention.

Actual housings were ultimately tested to more than 600 fastening andloosening events of greater than necessary torque. Additionally, ahandpiece was tested beyond rated torque events following more the 220autoclaves, where weathering and embrittlement could occur. Given thatthe torque applied without use of the torque base has been accommodatedto greater than 200 rated uses, there is a high degree of certainty thatthe failure mode of twisting the transducer in the housing has beeneliminated. The hexacog enables in excess of 200 torque events atgreater than rated torque, where previously even single or few errantevents could cause failure.

While several inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

The embodiments may be embodied in other forms without departure fromthe scope and essential characteristics thereof. The embodimentsdescribed therefore are to be considered in all respects as illustrativeand not restrictive. Although the present invention has been describedin terms of certain preferred embodiments, other embodiments that areapparent to those of ordinary skill in the art are also within the scopeof the invention.

We claim:
 1. A surgical handpiece for an ultrasonic surgical apparatus,comprising: a housing having an elongated body along a longitudinalaxis; a thermal diffuser comprising a thermal conductive layer and anelectrical insulating layer, wherein both the thermal conductive layerand the electrical insulating layer are disposed on the body of thehousing, wherein the electrical insulating layer is closer to thelongitudinal axis than the thermal conductive layer; wherein the thermalconductive layer includes two or more thermal conductive material piecescombining to form a first inner circumference and a first outercircumference, wherein each one of the two or more thermal conductivematerial pieces includes a length, an inner radius, and an outer radius;and wherein at least a portion of a circumference of the two or morethermal conductive material pieces includes an overlapping areatherebetween.
 2. The surgical handpiece of claim 1, wherein the thermaldiffuser is in a cylindrical or partially cylindrical form that fits inthe elongated body of the housing around the longitudinal axis.
 3. Thesurgical handpiece of claim 1, wherein the thermal conductive layer ismade of a material selected from the group consisting of copper,aluminum, nickel, silver, gold and alloys thereof.
 4. The surgicalhandpiece of claim 1, wherein the electrical insulating layer is made ofa material selected from the group consisting ofpolytetrafluoroethylene, polycarbonate, polypropylene and combinationsthereof.
 5. The surgical handpiece of claim 1, wherein the thermalconductive layer and the electrical insulating layer are bonded with anadhesive.
 6. The surgical handpiece of claim 1, wherein the housing ismade of an electrical insulating material.
 7. A surgical handpiece foran ultrasonic surgical apparatus, comprising: a housing having anelongated body along a longitudinal axis; a thermal diffuser comprisinga thermal conductive layer and an electrical insulating layer, whereinboth the thermal conductive layer and the electrical insulating layerare disposed on the body of the housing, wherein the electricalinsulating layer is closer to the longitudinal axis than the thermalconductive layer; wherein the thermal conductive layer includes two ormore thermal conductive material pieces combining to form a first innercircumference and a first outer circumference, wherein each one of thetwo or more thermal conductive material pieces includes a length, aninner radius, and an outer radius; and at least one of the two or morethermal conductive material pieces includes a second inner circumferenceand a second outer circumference and at least one of the two or morethermal conductive material pieces includes a third inner circumferenceand a third outer circumference, wherein at least a portion of thelength of adjacent thermal conductive material pieces overlap the secondinner circumference with the third outer circumference, and wherein theelectrical insulating layer is disposed along the second innercircumference and the third inner circumference of the two or morethermal conductive material pieces forming the first innercircumference.
 8. The surgical handpiece of claim 7, wherein the fulllength of the adjacent thermal conductive material pieces overlap. 9.The surgical handpiece of claim 7, wherein the second innercircumference abuts the third outer circumference of the overlappingadjacent thermal conductive material pieces.
 10. The surgical handpieceof claim 7 wherein the thermal conductive layer is made of at leastcopper and the electrical insulating layer is made of at leastpolytetrafluoroethylene.
 11. The surgical handpiece of claim 7, whereinthe thermal conductive layer and the electrical insulating layer arebonded with an adhesive.
 12. An ultrasonic surgical apparatuscomprising: a housing; an ultrasonically powered transducer within thehousing; a thermal diffuser comprising a thermal conductive layer and anelectrical insulating layer, wherein both the thermal conductive layerand the electrical insulating layer are disposed between the housing andthe transducer, wherein the thermal conductive layer is closer to thehousing than the electrical insulating layer; wherein the thermalconductive layer includes two or more thermal conductive material piecescombining to form a first inner circumference and a first outercircumference, wherein each one of the two or more thermal conductivematerial pieces includes a length, an inner radius, and an outer radius;and wherein at least a portion of a circumference of the two or morethermal conductive material pieces includes an overlapping areatherebetween.
 13. The apparatus of claim 12, wherein the housing has anelongated body and the thermal diffuser is in a cylindrical or partiallycylindrical form that fits in the elongated body around the transducer.14. The apparatus of claim 12, wherein the thermal conductive layer ismade of a material selected from the group consisting of copper,aluminum, nickel, silver, gold and alloys thereof.
 15. The apparatus ofclaim 12, wherein the electrical insulating layer is made of a materialselected from the group consisting of polytetrafluoroethylene,polycarbonate, polypropylene and combinations thereof.
 16. The apparatusof claim 12, wherein the thermal conductive layer and the electricalinsulating layer are bonded with an adhesive.
 17. The apparatus of claim12, wherein the housing is made of an electrical insulating material.18. The apparatus of claim 12, further comprising an ultrasonic horncontained within the housing.
 19. The apparatus of claim 18, wherein thehousing includes an inner surface, a longitudinal axis, and a housingengagement portion on the inner surface, the housing engagement portionhaving a transverse section that includes a central recess, a pluralityof pointed recesses pointing radially outward from the central recessand spaced evenly about the longitudinal axis, and convex arcs joiningadjacent pointed recesses; wherein the ultrasonic horn includes an outersurface and a horn engagement portion on the outer surface, the hornengagement portion having a transverse section that includes a centralportion, a plurality of pointed protrusions extending radially outwardand spaced evenly about the longitudinal axis, and concave arcs joiningadjacent pointed protrusions; and wherein each of the pointedprotrusions corresponds in shape and is engageable with each of thepointed recesses.
 20. The apparatus of claim 19, wherein at least onepointed recess has a recess tip portion that is rounded or curved orconstitutes a portion of a sphere.
 21. The apparatus of claim 19,wherein at least one pointed protrusion has a protrusion tip portionthat is rounded or curved or constitutes a portion of a sphere.